1. Field of the Invention
The present invention relates to an ultrasound medical treatment apparatus for treating a treatment target by irradiating intense focused ultrasound from outside of a patient, and an ultrasonic medical treatment apparatus utilizing an imaging device.
2. Description of the Background Art
The conventional non-invasive temperature measurement for an interior of the patient using temperature dependent magnetic resonance (MR) parameters used in ultrasound medical treatment requires complete data of both the positional relationship of the patient's organs and the temperature coefficients for the organs. Moreover, when precision of the temperature needs to be improved in order to improve the signal/noise ratio, spatial resolution must be sacrificed. Thus, non-invasive temperature measurement has been inappropriate for hyperthermia which requires high spatial and temperature resolutions.
Also, when a temperature change occurs in the measurement target, the measured MR parameters change because of their own temperature dependency. A change of the MR image due to degeneration thus can be obscured, and accurate judgement of the treatment's effect cannot be made. The treatment may be ended prematurely or applied excessively. Moreover, the efficiency of the treatment is lowered, and normal tissues can be affected.
Further, where significant motion occurs such as respiratory motion or heart beat motion, a danger arises because the focal point of the radiation applied to a treatment target during ultrasound medical treatment is displaced, and the normal tissues can be damaged. Moreover, in a case of treating a relatively large treatment target, such as cancerous tissue, by a scanning technique having a very small focal point, the scanning plan (treatment plan) can be spoiled, and the radiation position may be overlooked.
Furthermore, when an ultrasound imaging device is incorporated, real time continuous monitoring of treatment becomes possible. But, the ultrasound imaging device can only provide a two-dimensional tomographic image, so that anything off the tomographic plane cannot be handled. Moreover, the ultrasound imaging device has low resolution so that high precision setting of the focal point is difficult, and it has been very difficult to trace a narrow region accurately.
Now, in an ultrasound medical treatment apparatus, it is important to irradiate only the treatment target with intense ultrasound and not to affect the normal tissues. However, when tissues having different acoustic impedances are present on the ultrasound's irradiation route, refraction and reflection can occur, which displaces the focal point. Also, when an object with considerably different acoustic impedance, such as bone, lung, and clearance (intestinal gas), is present, further propagation of ultrasound to the treatment target can be prevented. Heat generation due to energy absorption occurs at such a position and may cause unexpected tissue degeneration.
Also, a tumor contains more blood vessels than normal tissues, and when irradiation with intense energy occurs, blood vessels can be damaged, and severe loss of blood can be caused.
Moreover, conventional techniques have not taken into account the change of the acoustic characteristic of thermally degenerated tissues.
In addition, during treatment with intense ultrasound radiation, cases have occurred in which the patient abruptly moves by sensing intense pain or heat, or for some other reason. In such a case, the focal point of the intense ultrasound is displaced from the intended position so that there is a danger of damaging normal tissues.
In ultrasound medical treatment, there is a need to monitor the treatment region and the ultrasound transducer. Ultrasound imaging is suitable for this purpose as it can provide real time monitoring. However, ultrasound imaging can be affected by noise due to the ultrasound irradiation used in ultrasound medical treatment so that monitoring during the treatment cannot be made. Even when intermittent ultrasound irradiation is adopted to cope with this problem, the real time feature cannot be realized, and accurate ultrasound irradiation has been difficult due to body movement and respiratory motion.